The present invention relates to magnetoresistive (MR) sensing mechanisms, which may for example be employed in information storage systems or measurement and testing systems.
FIG. 1 shows a media-facing view of a prior art magnetoresistive (MR) sensor 20 that may for example be used in a head of a disk drive. A MR structure 22 is formed including one or more ferromagnetic layers so that the structure 22 has a resistance that varies in response to an applied magnetic field. Lead layers 25 have been formed that carry current through the MR structure 22 to gauge the change in resistance and thereby sense the magnetic field. Bias layers 27 abut the structure to stabilize magnetic domains at the edges of the MR structure 22 and reduce noise in the sensor 100. A pair of magnetically soft shield layers 30 and 33 block stray magnetic fields from the MR structure 22, although fields that originate from the media opposite the MR structure 22 are not blocked by the shields. The shields 30 and 33 are isolated from the MR structure 22, leads 25 and bias layers 27 by first and second dielectric read layers 35 and 38.
The lead layers 25 may be made of gold that has been formed atop a tantalum seed layer and capped with another thin tantalum layer. The lead layers 25 overlap the MR structure 22 to contact the MR structure 22 at sharp points 40 and 42. Because the lead layers 25 overlap the MR structure 22, the effective sensing width of the sensor 20 is less than the width of the MR structure 22. The distance between the lead layers is sometimes called the track-width of the sensor 20. The electric current that flows through the MR structure 22 primarily flows through points 40 and 42, which can cause excessive heating at those points, reducing the sensitivity of the sensor and leading to other problems such as electromigration and damage to the sensor.